2025 USA-NA-AIO Round 1, Problem 3, Part 8

AI Olympiads 2025 USA-NA-AIO Round 1
1

Part 8 (5 points, coding task)

Do the following tasks in this part.

  1. Define a function called my_train_test_split that splits the whole dataset into the training component and the test/validation component.

    • The split is random

    • Inputs

      • X: A DataFrame object of features of all sample data.

      • y: A Series object of labels of all sample data.

      • test_size: It takes a value between 0 and 1 that denotes the fraction of samples used for testing. That is, the number of samples used for testing is int(total number of samples * test_size).

    • Outputs

      • X_train: It keeps samples in X for training.

      • X_test: It keeps samples in X for testing.

      • y_train: It keeps samples in y for training.

      • y_test: It keeps samples in y for testing.

  2. Call this function with inputs

    • X = X

    • y = y

    • test_state = 0.2

  3. Print object types and shapes of X_train, X_test, y_train, y_test.

2 
### WRITE YOUR SOLUTION HERE ###
def my_train_test_split(X, y, test_size):
    num_samples = X.shape[0]
    num_test_samples = int(num_samples * test_size)
    indices = np.random.permutation(num_samples)
    test_indices = indices[:num_test_samples]
    train_indices = indices[num_test_samples:]

    X_train = X.iloc[train_indices]
    X_test = X.iloc[test_indices]
    y_train = y.iloc[train_indices]
    y_test = y.iloc[test_indices]

    return X_train, X_test, y_train, y_test

X_train, X_test, y_train, y_test = my_train_test_split(X, y, 0.2)

print(type(X_train))
print(type(X_test))
print(type(y_train))
print(type(y_test))

print(X_train.shape)
print(X_test.shape)
print(y_train.shape)
print(y_test.shape)

""" END OF THIS PART """